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Biomedical subjects

R Renneberg

Publications and source records attributed to R Renneberg.

At least 19 recordsLinked to original sources
PubMed1999

Measurement of biodegradable substances using the salt-tolerant yeast Arxula adeninivorans for a microbial sensor immobilized with poly(carbamoyl)sulfonate (PCS). Part II: Application of the novel biosensor to real samples from coastal and island regions.

A microbial sensor for rapid measurement of the amount of biodegradable substances based on the salt-tolerant yeast Arxula adeninivorans LS3 has been developed especially for coastal and island regions. Our parameter, the so-called sensorBOD, that is available after only a few minutes, agrees with the 5-day value for the biochemical oxygen demand (BOD5) very well. We have employed the Arxula sensor in the short-time estimation and supervision of the BOD of both domestic and industrial wastewater with high salinity. The novel sensor makes it possible to monitor the different types of wastewater rapidly without pretreatment, and it can be used for an active process control of sewage treatment works. Compared to a commercially available sensor, the novel sensor achieves better agreement between sensorBOD and BOD5 measurements with salt containing samples.

Ascomycota↗
PubMed1999

Measurement of biodegradable substances using the salt-tolerant yeast Arxula adeninivorans for a microbial sensor immobilized with poly(carbamoyl) sulfonate (PCS) Part I: Construction and characterization of the microbial sensor.

A microbial biosensor based on the yeast Arxula adeninivorans LS3 has been developed for measurement of biodegradable substances. Arxula is immobilized in the hydrogel poly(carbamoyl) sulfonate (PCS). The immobilized yeast membrane is placed in front of an oxygen electrode with -600 mV versus Ag/AgCl. Arxula is salt tolerant; it can give a stable signal up to 2.5 M NaCl in sample (120 mM in measuring cell). The sensor's measurements are highly correlated to BOD5 measurements. It has a very high stability which can last for 40 day without any decrease in signal. The linear range of the sensor is up to a corresponding BOD value of 550 mg/l.

Biodegradation, Environmental↗
PubMed1998

Surface investigations on the development of a direct optical immunosensor.

In the present paper surface studies for the development of a direct optical immunosensor for fast diagnosis of a myocardial infarction are presented. A fatty acid binding protein was detected by monoclonal antibodies. The applied measuring system was the grating coupler BIOS-1. Based on commercially available transducer materials protein immobilisation techniques have been developed and characterised by TOF-SIMS, AFM and EM. Three different label-free assay types were investigated. Only one assay leads to a sensitive and regenerable sensor set-up. It was possible to detect concentrations of the fatty acid binding protein down to 330 ng/ml. The general applicability of a direct optical immunosensor in the field of myocardial infarction diagnosis was demonstrated by this.

Antibodies, Monoclonal↗
PubMed1998

On-line flow displacement immunoassay for fatty acid-binding protein.

In standard displacement flow immunoassays the analyte in the sample creates an active dissociation of labelled antigens (or antigen homologues) from an antigen binding site of an immobilized antibody, after which the labelled substance is measured downstream. Such systems have been described for molecules up to 1 kDa. In this study, we demonstrate displacement in a flow system for the detection of a small protein, cytoplasmic heart-type fatty acid-binding protein (15 kDa), a plasma marker for myocardial injury. The displacement system uses an inverse set-up: enzyme labelled monoclonal antibodies are associated to immobilized antigen, and are displaced by analyte in the sample. The system permits detection of both physiological (2-12 microg l(-1)) and pathological concentrations (12-2000 microg l(-1)) of fatty acid-binding protein in an on-line flow system.

Animals↗
PubMed1998

Kinetic analysis of immunointeractions with covalently immobilized fatty acid-binding protein using a grating coupler sensor.

Application of a grating coupler sensor (GCS) to the real time investigation of the interaction kinetics of covalently immobilized recombinant bovine heart-type fatty acid-binding protein (H-FABP) and corresponding antibody is described. The immobilization of the antigen is performed by activating the matrix hydroxyl groups with p-toluenesulfonyl chloride (TSC) and afterwards coupling the protein by reaction with its nucleophilic aminogroups. Covalent coupling via TSC permits reproducible measurements of immunointeractions on the same grating coupler sensor chip and complete regeneration after each binding cycle with glycine-hydrochloride. We demonstrate the analysis of binding data obtained on a GCS by linearization as well as direct curve fitting using the integrated rate equation for the determination of apparent rate and affinity constants. With both analysis methods we studied H-FABP/monoclonal anti-H-FABP-antibody interactions and obtained an average apparent association rate constant ka = 4.2 X 10(3) M(-1) s(-1) a dissociation rate constant of kd=1.3 X 10(-4) s(-1) and an equilibrium constant of KD=3 X 10(-8) M.

Animals↗
PubMed1997

Highly sensitive determination of hydrogen peroxide and peroxidase with tetrathiafulvalene-based electrodes and the application in immunosensing.

Redox mediators enable an efficient electron transfer between redox enzymes and the electrochemical surface of amperometric sensors. A stable and highly sensitive signal was obtained using a tetrathiafulvalene (TTF)-modified graphite electrode. In the presence of horseradish peroxidase (HRP), hydrogen peroxide (H2O2) was monitored with a detection limit of 7 nM at a potential of +20 mV versus a saturated calomel electrode (SCE). With a constant concentration of H2O2, the detection limit for HRP was found to be 150 pM. The accuracy of consecutive measurement of HRP in flow-through systems was improved by short-time polarizing the TTF-modified graphite electrode at +100 mV versus Ag/AgCl/3 M KCl. Using the TTF-modified graphite electrode in an immuno-sandwich approach, rabbit-immunoglobulin G was monitored in the range 5-100 ng/ml.

Animals↗
PubMed1995

Development of a heterogeneous amperometric immunosensor for the determination of apolipoprotein E in serum.

Apolipoprotein (apo) E is a constituent of serum lipoproteins and can serve as a diagnostic parameter for the assessment of disorders of lipid metabolism. For the determination of apo E in serum a sandwich-type amperometric immunosensor using disposable membranes was developed. The best results were obtained by using a site-directed attachment of a monoclonal capture antibody to a hydrazide-functionalized membrane surface. Bound antigen was then determined with the aid of a polyclonal antibody labelled with alkaline phosphatase in conjunction with p-aminophenyl phosphate as substrate. In this approach a carbon working electrode (vs. Hg/HgCl2) was used, and enzymatically generated p-aminophenol could be monitored with a detection limit of 40 pmol and a linear range of 26-20000 nM. The sensor displayed a linear response from 50 to 1000 ng ml-1 apo E. In contrast, antibody coupling through primary amino groups led to a total loss of antigen binding capacity in this assay configuration. The approach with site-directed immobilization however, not only allowed the determination of apo E in serum, but also the determination of antibody cross-reactivity against the apolipoproteins AI, AII and B.

Aminophenols↗
PubMed1991

Enzyme sensor-FIA-system for on-line monitoring of glucose, lactate and glutamine in animal cell cultures.

Enzyme sensors for glucose, lactate and glutamine were connected via flow-injection analysis (FIA) devices to two different bioprocesses. They were used for on-line process control of perfused bioreactor systems containing mammalian cell lines producing a monoclonal antibody and recombinant interleukin-2. The biosensor system gives direct access to important process data which can be used as control parameters for long term cell cultivation systems.

Animals↗
PubMed1991

Second generation biosensors.

Enzyme-membrane electrodes using glucose oxidase in combination with peroxide detection dominate in the field of laboratory analyzers for diluted samples. Using the same indication principle, extremely fast responding glucose sensors have been fabricated by covering thin metal electrodes with a porous enzyme layer. In the second generation auxiliary enzymes and/or co-reactants are coimmobilized with the analyte converting enzyme in order to improve the analytical quality and to simplify the performance. Following this line oxidizable interferences are suppressed by using a glucose oxidase/peroxidase complex which communicates with the electrode at a low working potential. Furthermore, fluctuations of pH or buffer capacity are ineffective when using a glucose oxidase/peroxidase layer covered fluoride FET in the potentiometric glucose determination. Enzymatic recycling of the analyte and/or accumulation of intermediates increase the sensitivity by several orders of magnitude. Inclusion of NAD bound to PEG in the glucose dehydrogenase layer allows a reagentless glucose measurement.

Biosensing Techniques↗
PubMed1985

An electrochemical method for determination of cell respiration.

The respiration of microorganisms was determined with a sensor composed of microorganisms and an oxygen electrode. The microorganisms (suspensions of about 100 microliters) are sedimented by centrifugation in a special tube on a very thin paper layer (diameter 4 mm). This paper layer is sandwiched between a polyethylene membrane and a dialysis membrane. A linear relationship is obtained between the current and the cell mass of Bacillus subtilis (between 0.05-0.35 mg dry weight per electrode preparation). When an assimilable substrate is added to the measuring solution the respiration rate is increased. It is possible to determine very fast changes in the respiration rates (1-5 sec). The application of this electrode system for investigations of the physiological state of cells during the growth cyclus is demonstrated.

Bacillus subtilis↗
PubMed1983

Study of H2O2-supported N-demethylations catalyzed by cytochrome P-450 and horseradish peroxidase.

H2O2-supported oxidative demethylation reactions catalyzed by cytochrome P-450 and horseradish peroxidase have been compared. In contrast to peroxidase catalyzed reactions no free substrate radicals could be detected by EPR stopped flow measurements in demethylation reactions catalyzed by highly purified cytochrome P-450 although the rate of product formation for both enzyme systems was identical. These findings cause doubts in a general peroxide dependent demethylation mechanism valid for all hemoproteins and in the hypothesis that free substrate radicals are principally formed during cytochrome P-450 catalysis.

Aminopyrine↗
PubMed1979

Comparison of the peroxidatic activity of cytochrome P-450 with other hemoproteins and model compounds.

The H2O2 dependent catalysis of cytochrome P-450 was compared with the catalytic mechanism of horse radish peroxidase, methemoglobin and iron protoporphyrin complexes. A relatively stable intermediate being comparable to compound I of horse radish peroxidase is formed in the case of iron porphyrin complexes, methemoglobin and probably cytochrome P-450. In the case of peroxidase compound II is the more stable intermediate. This could be the reason for the different catalytic properties of peroxidase on the one hand and iron porphyrin complexes, methemoglobin and cytochrome P-450 on the other hand.

Animals↗
PubMed1979

Electrochemical investigations on the oxygen activation by cytochrome P-450.

The application of cytochrome P-450 in substrate conversion is complicated both due to the limited stability and the cofactor regeneration problems. To overcome the disadvantages of NADPH consumption the transfer of the reduction equivalents from an electrode into the cytochrome P-450-system was studied: 1. NADPH was cathodically reduced at a mercury pool electrode. By immobilization of NADP on dialdehyde Sephadex the reductive recycling was possible. 2. Different forms of reduced oxygen were produced by the cathode: a) The reaction of O2- with deoxycorticosterone yields a carboxylic acid derivative. In contrast the cytochrome P-450 catalyzed NADPH-dependent reaction with the same substrate gives corticosterone, O2- represents only an intermediate in the activation of oxygen and is not the "activated oxygen" species. b) Molecular oxygen was reduced to HO2- and H2O2, respectively. The interaction of adsorbed cytochrome P-450 on the electrode surface with the reduced oxygen species in the absence of NADPH was studied. The electrochemically generated peroxide seems to be more active than added H2O2. 3. In a model of electro-enzyme-reactor several substrates were hydroxylated by microsomal cytochrome P-450 with cathodically reduced oxygen which substitutes NADPH.

Animals↗